Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$32.76	13.405%	$37.1515	$37.15	$37.15	$37.20
Purchase #2	$54.80	10.420%	$60.5102	$60.51	$60.50	$60.50
Purchase #3	$241.51	7.511%	$259.6498	$259.65	$259.65	$259.60
Purchase #4	$47.30	7.715%	$50.9492	$50.95	$50.95	$50.90
Purchase #5	$138.37	13.357%	$156.8521	$156.85	$156.85	$156.90
Purchase #6	$27.57	7.508%	$29.64	$29.64	$29.65	$29.60
Purchase #7	$166.46	13.873%	$189.553	$189.55	$189.55	$189.60
7 purchase totals =	$708.77		$784.3058	$784.30	$784.30	$784.30